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OpenCV C++ 畸變矯正、透視變換加速

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前兩周，同事和我說檢測時間超時，其中對圖像做畸變矯正和投影變換就要花費25ms（3000×3000的圖） 。而此時我們已經用上了文章opencv圖像畸變矯正加速、透視變換加速方法總結中的方法 。突然我想到了我去年筆記OpenCV筆記（10） 相機模型與標定中的一個函數cv::undistortPoints()，對感興趣點進行畸變矯正 。在應用之前，需要測試下兩種方法計算出來的點的差值 ， 即remap和undistortPoints的不同 。結論：對全圖進行畸變矯正，再找點 VS 找點后，對點進行畸變矯正，兩者的差值小于0.1個像素 ， 可行！同樣的方法可以運用在投影變換上 。在尺寸測量方面，這樣可以節省掉畸變矯正和投影變換的時間 。
1 只對感興趣的點進行畸變矯正// 讀取相機參數文件FileStorage fs("D:/distortionLens.xml", FileStorage::READ);Mat intrinsic_matrix = Mat(3, 3, CV_32FC1, Scalar::all(0));Mat distortion_coeffs = Mat(1, 5, CV_32FC1, Scalar::all(0));fs["intrinsic_matrix"] >> intrinsic_matrix;fs["distortion_coeffs"] >> distortion_coeffs;Mat mapx = Mat(s, CV_32FC1);Mat mapy = Mat(s, CV_32FC1);// 根據內參和畸變系數，建立查找表//intrinsic_matrix = getOptimalNewCameraMatrix(intrinsic_matrix, distortion_coeffs, s, 1, s, 0);initUndistortRectifyMap(intrinsic_matrix, distortion_coeffs, Mat(),intrinsic_matrix, s, CV_32FC1, mapx, mapy);// 方法1：畸變矯正后找角點Mat distortionMat;remap(src, distortionMat, mapx, mapy, INTER_CUBIC);vector<Point2f> distortPoints;findChessboardCornersSB(src, Size(21, 21), distortPoints, 64);// 方法2：找角點后畸變矯正vector<Point2f> oriPoints, sparsePoints;findChessboardCornersSB(src, Size(21, 21), oriPoints, 64);undistortPoints(oriPoints, sparsePoints, intrinsic_matrix, distortion_coeffs, Mat(), intrinsic_matrix);// 打印比較cout << "原圖找角點" << "\t" << "原圖remap后找角點" << "\t" << "對原圖角點矯正" << endl;for (int i = 0; i < sparsePoints.size(); i++) {cout << oriPoints[i] << "\t" << distortPoints[i] << "\t" << sparsePoints[i] << "\t" << "差值：" << distortPoints[i] - sparsePoints[i] << endl;}【OpenCV C++ 畸變矯正、透視變換加速】部分數據如下所示，可以看出，兩者差值小于0.1個像素，加速10ms完成，接下來再對投影變換加速一下 。

OpenCV C++ 畸變矯正、透視變換加速

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2 只對感興趣的點進行投影變換// 讀取變換矩陣fs = FileStorage("D:/transMat.txt", FileStorage::READ);Mat transMat = Mat(3, 3, CV_32FC1, Scalar::all(0));fs["transMat"] >> transMat;// 方法1：進行透視變換后找角點Mat warpMat;warpPerspective(src, warpMat, transMat, s, INTER_LINEAR, BORDER_CONSTANT, Scalar(255));vector<Point2f> warpPoints;findChessboardCornersSB(warpMat,Size(21, 21), warpPoints, 64);// 方法2：找角點后進行透視變換vector<Point2f> outPoints;for (int i = 0; i < oriPoints.size(); i++) { Mat_<double> oriPoint(3, 1); oriPoint(0, 0) = oriPoints[i].x; oriPoint(1, 0) = oriPoints[i].y; oriPoint(2, 0) = 1; Mat dstPoints = transMat * oriPoint; double a1 = dstPoints.at<double>(0, 0); double a2 = dstPoints.at<double>(1, 0); double a3 = dstPoints.at<double>(2, 0); outPoints.push_back(Point2f(a1 * 1.0 / a3, a2 * 1.0 / a3));}//打印cout << "原圖找角點" << "\t" << "原圖透視變換后找角點" << "\t" << "對原圖角點變換" << endl;for (int i = 0; i < sparsePoints.size(); i++) { cout << oriPoints[i] << "\t" << warpPoints[i] << "\t" << outPoints[i] << "\t" << "差值：" << distortPoints[i] - sparsePoints[i] << endl;}
OpenCV C++ 畸變矯正、透視變換加速

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3 合并3.1 讀取文件void GetMap(){ FileStorage fs(path+"distortionLens.xml", FileStorage::READ); if (fs.isOpened()) {intrinsic_matrix = Mat(3, 3, CV_64FC1, Scalar::all(0));distortion_coeffs = Mat(1, 5, CV_64FC1, Scalar::all(0));fs["intrinsic_matrix"] >> intrinsic_matrix;fs["distortion_coeffs"] >> distortion_coeffs; } fs = FileStorage(path+"transMat.txt", FileStorage::READ); if (fs.isOpened()) {transMat = Mat(3, 3, CV_64FC1, Scalar::all(0));fs["transMat"] >> transMat; }}3.2 變換感興趣點void remapPoints(vector<Point2f>& points) { for (int i = 0; i < points.size(); i++) {Mat_<double> oriPoint(3, 1);oriPoint(0, 0) = points[i].x;oriPoint(1, 0) = points[i].y;oriPoint(2, 0) = 1;Mat dstPoint = transMat * oriPoint;double a1 = dstPoint.at<double>(0, 0);double a2 = dstPoint.at<double>(1, 0);double a3 = dstPoint.at<double>(2, 0);points[i] = Point2f(a1 * 1.0 / a3, a2 * 1.0 / a3); } undistortPoints(points, points, intrinsic_matrix, distortion_coeffs, Mat(), intrinsic_matrix);}

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